1. Field
The present disclosure relates generally to electrical power systems, such as systems for generating and distributing electrical power on an aircraft. The present disclosure relates more specifically to identifying undesired conditions, such as arc faults, in such power systems and protecting such systems from such undesired conditions in a coordinated manner.
2. Background
Aircraft may employ various electronic devices and systems to perform various functions on the aircraft. Power for the electronic devices and systems on an aircraft may be provided by an aircraft power system. The aircraft power system may include a number of generators along with various power distribution and conversion systems. For example, a number of generators may be driven by the aircraft engines. Feeder lines may carry generated power from the generators to the various power distribution and conversion systems.
Power conversion systems on aircraft may include, for example, rectifiers and transformers. Rectifiers may be used to provide direct current (DC) power from the alternating current (AC) power provided by the generators. Transformers may be used to provide various levels of AC and DC power. Power distribution systems on aircraft may include AC and DC buses and various feeder lines for carrying power between the buses and between the buses and various loads on the aircraft.
It is desirable to protect the components of an aircraft power system from undesirable conditions that may occur on the power system. An example of such an undesirable condition is a fault condition that results in an arcing event. An arc fault is a discharge of electricity between two or more conductors. This discharge releases heat, which may break down insulation and possibly trigger an electrical fire. The strength and duration of arc faults may be highly variable. For example, an arc fault may be caused in an aircraft power system by debris entering a power panel or another part of the power system.
Traditional commercial aircraft typically employ relatively low voltage, fixed frequency power systems. Such systems are relatively less susceptible to arc faults. Testing has shown that it is relatively difficult to establish arcs in traditional aircraft power systems. Protection from faults in such power systems may be implemented using current transformers. All bus and load distribution wiring may be fed through these current transformers.
Modern aircraft power systems may operate at higher voltage and frequency levels than traditional aircraft power systems. For example, voltages may be greater than 115 Vrms AC or DC and frequencies may be greater than 400 Hz. Due to the differences between traditional aircraft power systems and more modern systems, the methods for providing power system protection in traditional systems may not be used to provide the desired protection for more modern aircraft power systems.
Accordingly, it would be desirable to have a method and apparatus that takes into account one or more of the issues discussed above as well as possibly other issues.